Before the SDP world had ICE, the C line used to show the Media Address where the RTP could be sent.
But this did not help in ICE / NAT Traversal cases where the private and public IP are different. And add to that the need to use a TURN server in the case of asymmetric NAT.
Hence ICE has a bunch of parameter and most significantly the
The Host tag shows the Private IP - Can be reached by Peers in local networks
The Srflx tag shows the Public IP - If possible accessible by the whole outside world unless behind NAT
The relay tag that has the TURN IP - Which will loopback the media in case of asymmetric NAT's
This is the significance of the different ICE Candidates. There are a few more parameters, but this is major enhancements to the original SDP